It is commonly believed that Jack the Ripper murdered five women - often referred to as the "canonical five".The
first mention of the number of victims being limited to five was made
by Melville Leslie Macnaghten (appointed Assistant Chief Constable,
Metropolitan Police in June 1889, promoted to Chief Constable in 1890)
in a memo of 23 Feb 1894(now in the National Archives - Metropolitan Police files MEPO 3/140; first made known to the public in the book The Complete Jack the Ripper by Donald Rumbelow, published by W H Allen in 1975): After the
dreadful crimes so placidly
perpetrated in Mitre Square and Berner
street, I conceived an ardent desire to visit and see for myself the
region... ."Now the Whitechapel murderer had 5 victims - & 5 victims only - his murders were (i) 31st Aug `88. Mary Ann Nichols, at Buck`s Row, who was found with her throat cut & with (slight) stomach mutilation
(ii) 8th Sept `88. Annie Chapman - Hanbury Street, throat cut, stomach
& private parts badly mutilated & some of the entrails placed round the neck
(iii) 30th Sept `88. Elizabeth Stride, Berner`s Street, throat cut, but
nothing in shape of mutilation attempted & on same date Catherine Eddowes. Mitre Square, throat cut, & very bad mutilation,
both of face & stomach (iv) 9th November. Mary Jane Kelly. Miller`s Court. throat cut, and the whole body mutilated in the most ghastly manner".Macnaghten (appointed
Assistant Commissioner [Crime] in 1903, knighted in 1907, retired in
1913) re-iterated his claim of five victims in his memoirs in his book Days Of My Life, published by Edward Arnold in 1914:
Suffice it, at present, to say that the Whitechapel murderer committed
five murders, and - to give the devil his due - no more,

The term "canonical five" is credited, by researchers and authors Paul Begg and John Bennett, in Jack the Ripper: The Forgotten Victims, published by Yale University Press in 2013, to have been coined in 1987 by Martin Fido, researcher and author of The Crimes, Detection and Death of Jack the Ripper (Weidenfeld and Nicholson. 1987).